Distributed beamforming with limited feedback in regenerative cooperative networks
WiCOM'09 Proceedings of the 5th International Conference on Wireless communications, networking and mobile computing
Covariance based linear precoding in amplify-and-forward cooperative networks
ISCIT'09 Proceedings of the 9th international conference on Communications and information technologies
Effect of feedback delay on downlink amplify-and-forward relaying with beamforming
GLOBECOM'09 Proceedings of the 28th IEEE conference on Global telecommunications
GLOBECOM'09 Proceedings of the 28th IEEE conference on Global telecommunications
Low complexity receivers for coherent amplify-and-forward cooperative systems
IEEE Transactions on Communications
Mobile Networks and Applications
Synthesis and array processor realization of a 2-D IIR beam filter for wireless applications
IEEE Transactions on Very Large Scale Integration (VLSI) Systems
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A relay selection approach has previously been shown to outperform repetition-based scheduling for both amplify-and-forward (AF) and decode-and-forward (DF) cooperative networks. The selection method generally requires some feedback from the destination to the relays and the source, raising the issue of the interplay between performance and feedback rate. In this letter, we treat selection as an instance of limited feedback distributed beamforming in cooperative AF networks, and highlight the differences between transmit beamforming in a traditional multi-input single-output (MISO) system and the distributed case. Specifically, Grassmannian line packing (GLP) is no longer the optimal codebook design, and orthogonal codebooks are no longer equivalent to each other. We derive the high signal-to-noise ratio expressions for outage probability and probability of symbol error for unlimited-feedback and selection schemes, which are then used for performance comparisons. The selection protocol is compared to a limited-feedback distributed beamformer that assigns codebooks based on the Generalized Lloyd algorithm (GLA), and one that uses random beam-vectors. The main conclusion is that the performance improvement to be seen using the very complex GLA is small, and that many more feedback bits are required with random beamforming than selection for the same performance. These results indicate that the selection protocol is a very attractive protocol, with low complexity, that provides excellent performance relative to other known methods.